Metal surfaces require pretreatment before being coated with polymeric coatings such as paints, and the like. Without such pretreatment, adhesion of the coating is generally poor. Further, untreated metal surfaces, even when coated with a polymeric coating, may suffer severe corrosion.
Many different pretreatments have been utilized to provide corrosion prevention and improved adhesion. Chromium and phosphate pretreatments have been used, but are in disfavor. Silane treatment, as well as treatment with zirconium has also been suggested. In particular, a treatment combining an organofunctional silane with a zirconium compound and various acids has been used to provide corrosion prevention and to improve adhesion.
Such a coating composition is very acidic. Therefore, there is a tendency to form a sludge. Although this does not interfere with the quality of the treatment, it does create a waste disposal problem.